The disclosures herein relate generally to heart valves and more particularly to modular heart valves.
Heart valves generally include a grafting member such as a sewing cuff, a stiffening ring and a valve assembly. The valve assembly typically includes a valve body and one or more leaflets that are pivotally attached to the valve body. Unitary heart valves are inherently installed as a unitary device requiring mechanical attachment to the associated anatomy of the heart. The implantation of modular heart valves generally entails attaching the grafting member and then attaching the valve assembly.
A limitation of unitary heart valves is that the surgeon cannot readily view beyond this type of heart valve to check for any possible blockages or other anomalies. To view beyond the heart valve, the internal components of the valve assembly must be manually manipulated. The manipulation of the internal components generally entails placing a sharp instrument through the valve assembly. This presents a risk of damaging the internal components of the valve assembly.
Another limitation of integrated heart valves is the technique of securing the graft assembly to the annulus using sutures. This technique is time-consuming and occurs while the patient is on cardiac-by-pass. It is undesirable to keep a patient on cardiac-by-pass for an extended period of time.
Present modular heart valves suffer from one or more limitations. In some instances, present modular heart valves are expensive to manufacture due to costly process steps of forming complex shapes such as helical screw-type threads. Another common limitation is the difficulty in attaching the valve assembly to the grafting member. The space required for implanting these type of prosthetic devices is limited. With this being the case, complex attachment schemes are quite undesirable. U.S. Pat. No. 4,680,031 discloses a "tissue valve type" heart valve prosthesis which has a biocompatible plastic sewing ring adapted to be surgically implanted into the mitral, aortic or tricuspid annulus of the human heart. The sewing ring has internal square threads and a bio-compatible fabric mesh or cloth that is embedded into the sewing ring so that the cloth can be fully wrapped around the sewing ring covering all of its plastic surfaces except for the internally protruding threads. A bio-compatible plastic stent support ring has externally disposed threads to lock with the threads of the sewing ring in approximately one turn, or less. The stent support ring also embeds a bio-compatible fabric mesh which can be wrapped around the stent support ring to cover all of its plastic surfaces, except for the protruding threads, and to form a cloth pocket wherein a solid stent is mounted.
U.S. Pat. No. 5,607,465 discloses a valve for use in a blood vessel, internal to the blood vessel itself. The valve has a bent flexible wire mesh with elasticity and plasticity so as to be collapsible and implantable remotely at a desired site. The wire mesh is bent into three turns, two end ones and a central one, in such a way as to confine a tubular space. The central turn is located at an angle relative to the end turns and mounts a monocusp sail-like valving element. A special catheter is used to collapse the flexible wire mesh to implant it remotely at the desired site and to restore the wire mesh to its original three-dimensional configuration.
U.S. Pat. No. 5,716,370 discloses a technique for replacing a heart valve using minimally invasive methods to reduce the time associated with replacing the valve. This technique includes a sutureless sewing cuff and a fastener delivery tool that holds the cuff against the patient's tissue while delivering two fasteners. The fasteners are delivered two at a time in opposite directions to attach the cuff to the tissue from the inside out. Drawstrings are operated from outside the patient's body and cinch the sewing cuff to the valve body. The cuff is releasably mounted on the tool. The tool stores a plurality of fasteners thereon. Two rows of staggered fasteners are formed whereby fasteners are located continuously throughout the entire circumference of the cuff.
Although attempts have been made to modular heart valve prosthetic devices, to provide improved accessibility to the anatomy below an installed heart valve and to reduce the time required for implantation, these attempts have provided only limited success. Accordingly, there is a need for a heart valve that overcomes the shortcomings of present heart valve assemblies and implantation techniques.